Going straight to your questions:
1) You can display more than one series information inside a trackball info. Please, refer to this example to see how this is implemented: http://demos.telerik.com/silverlight/#ChartView/Financial
2) Yes, datetime is currently implemented as categorical. Have you considered/tried retemplating the candlestick template to include the needed marker?
The release is scheduled for the week of February 15th.
the Telerik team
Explore the entire Telerik portfolio by downloading the Ultimate Collection trial package. Get it now >>